AMINES AND AMIDES. CYANOGEN COMPOUNDS. 359 



etc. It is also found among the products of the destructive distilla- 

 tion of coal, and is formed by a great number of chemical decompo- 

 sitions. For instance: 



By passing ammonia over red-hot charcoal : 



4NH 3 -f 30 = 2(NH 4 CN) + CH 4 . 

 Ammonia. Carbon. Ammonium Methane, 



cyanide. 



By the action of ammonia on chloroform : 



CHC1 3 + NH 3 = HCN + 3HC1. 

 Chloroform. Hydrocyanic Hydrochloric 



acid. acid. 



By heating ammonium formate to 200 C. (392 F.) : 



NH 4 CH0 2 : HCN + 2H 2 O. 



Ammonium Hydrocyanic Water, 

 formate. acid. 



By the action of hydrosulphuric acid upon mercuric cyanide : 



Hg(CN 2 ) + H 2 S == HgS -f 2HCN. 

 By the decomposition of alkali cyanides by diluted acids : 



KCN -f- HC1 = KC1 -f HCN. 

 By the action of hydrochloric acid upon silver cyanide : 



AgCN -f HC1 = AgCl + HCN. 

 By distilling potassium ferrocyanide with diluted sulphuric acid : 



2K,Fe(CN) 6 + 6(H 2 S0 4 ) = K 2 Fe 2 (CN) 6 + 6KHSO, + 6HCN. 



Potassium Sulphuric Potassium ferrous Potassium acid Hydrocyanic 



ferrocyanide. acid. ferrocyanide. sulphate. acid. 



Experiment 55. Place 20 grammes of potassium ferrocyanide and 40 c.c. of 

 water into a boiling-flask of about 200 c.c. capacity ; provide the flask with a 

 funnel-tube and connect it with a suitable condenser, the exit of which should 

 dip into 60 c.c. of diluted alcohol, contained in a receiver, which latter should 

 be kept cold by ice during the operation. After having ascertained that all 

 the joints are tight, add through the funnel-tube a previously prepared mixture 

 of 15 grammes of sulphuric acid and 20 c.c. of water. Apply heat and slowly 

 distil until there is little liquid left with the salts remaining in the flask. 



Determine the strength of the alcoholic solution of hydrocyanic acid thus 

 prepared volumetrically and dilute it with water until it contains exactly two 

 per cent, of HCN. 



Pure hydrocyanic acid is, at a temperature below 26 C. (78.8 F.), 

 a colorless, mobile liquid, of a penetrating, characteristic odor resem- 

 bling that of bitter almonds ; it boils at 26.5 C. (80 F.) and crystal- 

 lizes at 15 C. (5 F.). It is readily soluble in water, and a 2 per 

 cent, solution is the diluted hydrocyanic acid, Acidum hydrocyanicum 

 dilutum. 



